Intracerebral hemorrhage (ICH) is the deadliest stroke subtype. Warfarin, a widely used anticoagulant for prevention of thromboembolic stroke, increases both risk and severity of ICH. Thus, even relatively minor elevations in risk for ICH on warfarin can sway the balance in favor of withholding treatment. Accumulated evidence points to a strong familial contribution to ICH susceptibility. Data from the investigators suggest warfarin-related ICH shares genetic risk factors with ICH in individuals not on warfarin. The identification of genetic risk factors for ICH may therefore offer novel biological insights, as well as provide immediate clinical impact by improving risk assessment for chronic anticoagulation. To discover genes involved in development of ICH and warfarin-related ICH, this proposal brings together a team of clinician-investigators with world-class expertise in the phenotyping and biology of ICH alongside geneticists who are among the world's preeminent experts in the methods and analysis of genome-wide data. The population of patients who will contribute are the most thoroughly characterized ICH cases and controls available, and have been assembled specifically for genetic and gene-environment studies. Subjects all have detailed data on warfarin dose, laboratory values including coagulation parameters, clinical history, neuroimaging and clinical follow-up. Specific aims are:1) To collect and curate data for >900,000 SNPs and 946,000 copy number probes in 1,000 cases with ICH unrelated to warfarin and 1,000 matched controls not taking warfarin; 2) To identify genetic variants associated with warfarin-related ICH, using data for >900,000 SNPs and 946,000 copy number probes in 500 cases of warfarin- related ICH and 1,000 matched controls taking warfarin, but without ICH; 3) To identify genetic variants that influence warfarin dose requirement in the same group of 500 cases of warfarin-related ICH and 1,000 matched controls. Replication of any association will be carried out in three additional independent datasets. Our study will thoroughly test the hypothesis that common variants play a major role in ICH, setting the stage for the future genetic study of this disease. The team's track record of cutting-edge research in the neuroimaging and epidemiology of ICH as well as in human genetic variation, along with our aggressive data release policy, will ensure that the substantial investment in phenotyping and genotyping is used for the widest possible benefit for present and future patients. Intracerebral hemorrhage (ICH) is the deadliest stroke subtype. Warfarin, a widely used anticoagulant for prevention of thromboembolic stroke, increases both risk and severity of ICH. This project aims to discover the genes that cause ICH in individuals on and off warfarin. It therefore offers the promise of novel biological insights, as well as immediate clinical impact through improving risk assessment for chronic anticoagulation.